Hydrothermal treatment of an agglomerate of synthetic mica crystals



nited stat p g fRoTHERMAL TREATMENT or A" tiIi'oM- ERATE F SYNTHETIC MICA CRYSTALS Tokiti'Noda, Los Angeles, Calit.

This invention relates to'a method of treating 'an agglomerate mass of crystals formed' frdm'a siliceous rhlt to render the individual crystal amenable to separation from the mass, and more particularly to arn'eth'od of treating an agglomerate mass of synthetic i'nica 'cfys 'als to render the individual crystals amenable to s'e'parati'cin from the mass and to improve the separated crystals.

Included among the objects and advantages is a process for hydrothermally treating a mass of crystals bound together by a siliceous impurity to render the individual crystals amenable to separation from the mass without breaking. The hydrothermal treatment devitrifie's the surface adhesive siliceous material so that the individual crystals are soft and pliable and suitable for punching, stamping and like operations. The "treatment may be use'd to-control the hydrolysis of mica crystals to 'cliang'e the characteristics of the mica. These and other objects and advantages may be readily understood by the followin'g'de'scription. In one method of making synthetic mica crystals, as for example, such as described in Japanese Pateiit No. 138,642, a mass or fluoro-phlo'gopite or its is'omdrph'ous substitutes are melted, from about l400 to 1500" C. or higher depending on the composition, and then rio moting'cry'stal growth in the melt at about the "cry lizati'on temperature large individual crystals or formed. 7 As the crystals form, however, they ronj iii an agglomerated mass interspersed with surplus component other than mica composition, which 'is :a siliceous "i'm'p'ur'ity, which forms in between the crystals arid on the surface of the individual mica crystals in the mass. The deleterious siliceous inclusion in the 'mica'naass is a glassy substance c'o'nipr'isii ng generally a silicate con taini'ng one or more of potassium, aluminum, magnesium andfluorine ions. The glassy inclusion bindsthe' mica crystals together in a mass and makes it diflicultto split the individual crystals from each other, and, further, the glassy substance adheres to the individualjc'ryst'als making them hard and brittle. lnfth is condition the crystals are not suitable for punching, stamping, die work, and the like. H

In accordance with the present invention I have 'dis'covie'red the process for treating a mass of an ag'glomerate of synthetic mica crystals for rendering the ind V mica crystals amenable to separation and for devitr'ifyfing the glassy inclusions to make the individual'cr'ystals pliable and easily worked. The process includes a hy} drotherr'nal treatment which is heating a mass ofthe synthetic mica crystals in water at 'an elevated temperature for a period of time to deteriorate by porrosios or Iwre treatd with a 2 N sodifim hyd'l X1 dy devitrification the glassy substance which adheres'rofafid binds the individual mica crystals. The process, also, includes a partial hydrolysis of the fluoro-phlog 'opit'ei 'to form a mica which is equivalent to natural phiagopit, or the hydrolysis may be suppressed in the treatment "th provide for the recovery ofthe fluoro phlogopiteprys tals. In the hydrothermal treatment of the synthetic "ice mica, the fluorine ion may be replaced 'by the hydroxyl ion under conditions of the treatment, and due to this hydrolysis the synthetic mica is converted to .very nearly the same composition as that of the natural mica. In certain instances, however, the hydrolysis may be dele teriou's to the mica,-sihce the fluoro'form is thermally stable Whereas the-hydrox'yl or the natural form is not. :The process, therefore, provides for suppression of the hydrolysis during the treatment when 'it is desired to recover the fluoro or synthetic forin of the mica.

The process in general contemplates heating a mass of an agglomerate of-syritlietic 'iriica crystalsin an autoclave'in' aqueous solution to temperaturesab'ove about C.-'for-a period'bf time extendin from several re 48 hours or more depending on the mass to betreate d. The mass may be hydrothermally'trea'ted in aqueous electrolytic solution to produce thecorrosion'or devitr ification of the deleterious inclusion in the mica crystal mass along with the hydrolysis where desirable. Where the fluororormoftlie mica crystals 'isdesir'ed, a hydrdlysis 'suppressem's included in the aqueous electrolyte seru- -tion. Such a hydrolysis suppressor may be fluorine compounds such as fluorides, fluosilicate's, and the like which suppress the hydrolysis.

The following examples will describe the invention in more 'detail:

Example I of synthetic 'mic rysms (flu'o'ro-l phlo'g opite) were treate'd with water at 350 C. for 24 hours in ra ars. The fluorine content of the iiritreated nia ss I 1 3% Ja'iid that or the treated blocks was Th e fluorine content proyides a measure of the action of the treatment o'n the individual mica crystals.) The tr 'ted blocks of the synthetic mica were easily seprated into individual crystals without breakage, and the crystals were sufliciently pliable to be suitable for punching, stamping, and like operations.

Example 11 fig elgserrhe similar crystalline massasdisclosedin like ple l w'ere treated with an aqueous 2 Nsodium hydr sblution a't 350; for 24 nea s. hegfl i si ent fthe 'treated 'blocks was 13.0%. The were readily splitin'to the individual mica crystals, and the crystals were soft and flexible.

Example III lar er; at the crystall ne ma er Si i la' steam-at I were treated in the 2 N sodium hydroxide solution at 350 for 48 hours. The crystalline mass split into the individual crystals. The fluorine content or the treated blocks had decreased to about 8.6%.

Example I Blocks of similar crystalline mass as illustrated Example-I were treated with a 2 N sodium hydroiide Serums ceirrain n 'a oarm sodiurn flu'o nfi at .351) for48 The fluorine content 'of the treated blocks were 11.2%. The mass was easily separated into iii 'dividual mica crystals.

Example V Blocks "of a similar crystalline mass as des solution Cli1tail1ifig5% Sodium flllOlO-Silitiltf: at 350? C. for 48 hours. The crystals were eas lyjsep arate d into individual crystals of mica, and the fluorine content of the treated blocks was By increasing the sodium fluoro silicate, the decrease of fluorine content could be made even smaller.

Example VI Blocks of synthetic mica crystalline mass as described in Example I were treated with a 1 N potassium hydroxide solution containing potassium fluoro-silicate (K2SiFs) at 250 C. for 24 hours. The splitting of a mass into individual crystals is easily accomplished.

Example VII Blocks of synthetic mica similar to that described in Example I is treated with a /2 N potassium hydroxide solution containing 5% potassium fluoride at 250 C. for 24 hours. The splitting of the block into individual crystals is greatly facilitated.

Example VIII Blocks of synthetic mica as described in Example I were treated with a 16 Npotassium carbonate solution at 250 C. for 24 hours. The splitting of the crystals from the block is easily accomplished.

After treating the synthetic crystalline mass, single crystals of mica may be easily split oil from the mass. The mica crystals may be separated from the mass without breaking the individual crystals which provides a good yield of large single individual crystals. The individual crystals are soft and elastic and substantially free from the glassy inclusion of the surface of the crystals. The soft elastic crystals are suitable for punching, stamping and other similar types of operation.

As described above, the decrease of fluorine content in the synthetic mica may be suppressed to a minimum when a suppressor is added to the reacting solution, so that substantially the same synthetic crystal may be recovered after the treatment. By reducing the hydrolysis of the fluoro-mica to a minimum the thermal stability, a characteristic property of synthetic mica, is not deteriorated. The suppressor may be used in amounts up to or more, depending on the composition of the mass, and with fluoro-phlogopite about 5% concentration of the fluorine compounds is sufficient to suppress the hydrolysis during the hydrothermal treatment.

The hydrothermal treatment of the synthetic crystalline mica blocks may be performed at the elevated temperatures either in water or an aqueous solution of electrolytes, such. as bases, acids, or salts. Since the action is carried out at elevated temperatures, the treatment is conducted in a closed vessel, such as an autoclave, bomb and the like to provide for the high temperatures and the resultant pressures of the super-heated aqueous reaction media.

The invention has been illustrated by specific examples but there is no intent to limit the invention to the specific details so disclosed, except insofar as set out in the following claims.

I claim:

1. The method of treating an agglomerate of synthetic mica' crystals and deleterious binding material prior to separating individual crystals therefrom which comprises superheating above about 100 degrees C. a mass of such an agglomerate of synthetic mica crystals in an aqueous solution in the presence of a soluble fluoride composition as a hydrolysis suppressor to render the mass amenable to separation into individual crystals and substantially remove the deleterious binding material from the crystals.

2. The method of treating an agglomerate of synthetic mica crystals and deleterious binding material prior to separating individual crystals therefrom which comprises superheating above about 100 degrees C. a mass of such an agglomerate of synthetic mica crystals in an aqueouselectrolyte solution in the presence of a soluble fluoride composition as a hydrolysis suppressor to render the mass amenable to separation into individual crystals and substantially remove the deleterious binding material from the crystals.

3. The method of treating an agglomerate of synthetic mica crystals and deleterious binding material prior to separating individual crystals which comprises superheating above about 100 degrees C. a mass of such an agglomerate of synthetic mica crystals in an aqueous alkaline solution in the presence of a soluble fluoride composition as a hydrolysis suppressor to render the mass amenable to separation into individual crystals and substantially remove the deleterious binding material from the crystals.

4. The method of treating an agglomerate of synthetic mica crystals prior to separating individual crystals therefrom which comprises heating a mass of such an agglomerate of synthetic mica crystals in water at about 350 C. for about twenty-four hours to devitrify the siliceous impurities binding said crystals and render them amenable to separation.

5. The method of treating an agglomerate of synthetic mica crystals prior to separating individual crystals therefrom which comprises heating in an autoclave a mass of such an agglomerate of synthetic mica crystals in an aqueous sodium hydroxide solution at temperatures above about 100 C., in the presence of a soluble fluorine compound as a hydrolysis suppressor.

6. The method of treating an agglomerate of synthetic mica crystals prior to separating individual crystals which comprises heating a mass of such an agglomerate of synthetic mica crystals in an aqueous electrolyte solution at temperatures above about 130 C., for a period of time sufficient to devitrify the deleterious crystal binding impurities and in the presence of a soluble fluorine compound as a hydrolysis suppressor.

7. The method of treating an agglomerate of synthetic mica crystals prior to separating individual crystals which comprises heating in an autoclave a mass of such an agglomerate of synthetic mica crystals in an aqueous sodium hydroxide solution at temperatures above about 100 C., for a period of time sui'licient to devitrify the deleterious crystal binding impurities and in the presence of sodium fluoride as a hydrolysis suppressor.

8. The method of treating an agglomerate of synthetic mica crystals prior to separating individual crystals which comprises heating in an autoclave a mass of such an agglomerate of synthetic mica crystal-s in a 2 N sodium hydroxide aqueous solution at temperatures above about 100 C., for a period of time sufiicient to devitrify the deleterious crystal binding material, and in the presence of five percent of sodium fiuorosilicate as a hydrolysis suppressor.

9. The method of treating an agglomerate of synthetic mica crystals formed from a siliceous melt and including siliceous impurities binding the mica crystals together which comprises superheating a mass of such an agglomerate of synthetic mica crystals in an alkaline solution substantially above degrees C. for an extended period of time so as to devitrify the siliceous impurities and render such mica crystals amenable to separation into large individual crystals.

10. The method of treating an agglomerate of synthetic mica crystals formed from a siliceous melt and including deleterious impurities binding the crystals together prior to separating individual crystals therefrom, which comprises superheating in an autoclave a mass of such synthetic mica crystals in an aqueous electrolyte solution above about 100 degrees C. for a sufficient time to devitrify the impurities binding the crystals and render them amenable to separation.

11. The method of treating an agglomerate of synthetic mica crystal-s formed from a siliceous melt and including deleterious impurities binding the crystals together prior to separating individual crystals therefrom. which comprises superheating in an autoclave a mass of such synthetic mica crystals in an aqueous electrolyte and soluble fluoride solution above about 100 degrees C. for a suflicient time to devitrify the impurities binding the crystals and render them amenable to separation.

v 12. The method of treating an agglomerate of synthetic mica crystals formed from a siliceous melt and including deleterious impurities binding the crystals together prior to separating individual crystals therefrom, which comprises superheating in an autoclave a mass of such synthetic mica crystals in an aqueous potassium hydroxide solution above about 100 degrees C. for a sufiicient time to devitrify the impurities binding the crystals and render them amenable to separation.

References Cited in the file of this patent UNITED STATES PATENTS 2,185,280 Stuckardt et a1. Ian. 2, 1940 6 2,516,983 Hatch Aug. 1, 1950 2,645,060 Waggoner July 14, 1953 2,549,880 Bardet Apr. 24, 1951 OTHER REFERENCES Kendall et aL: Proceeding of International Congress of Pure 'and Applied Chemistry, pages 167-170 (1947). Wyart et al.: Chem. Abstracts, vol. 44, 1950, column 7722. C. A. citing Compte Rendu, vol. 229, pages 

1. THE METHOD OF TREATING AN AGGLOMERATE OF SYNTHETIC MICA CRYSTALS AND DELETERIOUS BINDING MATERIAL PRIOR TO SEPARATING INDIVIDUAL CRYSTALS THEREFROM WHICH COMPRISES SUPERHEATING ABOVE ABOUT 100 DEGREES C. A MASS OF SUCH AN AGGLOMERATE OF SYNTHETIC MICA CRYSTALS IN AN AQUEOUS SOLUTION IN THE PRESENCE OF A SOLUBLE FLUORIDE COMPOSITION AS A HYDROLYSIS SUPPRESSOR TO RENDER THE MASS AMENABLE TO SEPARATION INTO INDIVIDUAL CRYSTALS AND SUBSTANTIALLY REMOVE THE DELETERIOUS BINDING MATERIAL FROM THE CRYSTALS. 